libbinder: make writeObject private

This API uses the binder kernel interface, which
is not exported. It's also pretty low level, so
just hide it.

Bug: N/A
Test: N/A
Change-Id: I256445ea6801be6bf909c3675e32c33c4a13a6d3

Author: Steven Moreland

libs/binder/include/binder/Parcel.h

@@ -401,8 +401,6 @@ class Parcel {
     // as long as it keeps a dup of the blob file descriptor handy for later.
     LIBBINDER_EXPORTED status_t writeDupImmutableBlobFileDescriptor(int fd);
 
-    LIBBINDER_EXPORTED status_t writeObject(const flat_binder_object& val, bool nullMetaData);
-
     // Like Parcel.java's writeNoException().  Just writes a zero int32.
     // Currently the native implementation doesn't do any of the StrictMode
     // stack gathering and serialization that the Java implementation does.
@@ -679,6 +677,7 @@ class Parcel {
     // Set the capacity to `desired`, truncating the Parcel if necessary.
     status_t            continueWrite(size_t desired);
     status_t truncateRpcObjects(size_t newObjectsSize);
+    status_t writeObject(const flat_binder_object& val, bool nullMetaData);
     status_t            writePointer(uintptr_t val);
     status_t            readPointer(uintptr_t *pArg) const;
     uintptr_t           readPointer() const;